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Re: [gpsd-dev] AIS NMEA TAG Blocks

From: Ed W
Subject: Re: [gpsd-dev] AIS NMEA TAG Blocks
Date: Thu, 28 Aug 2014 23:39:58 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.0


 From my personal experience, the way to know if a TAGblocked timestamp is in
seconds or milliseconds is ask the people in charge of setting up the
device/service. Perhaps some devices output only secs/msecs, and some other
accept the NMEA 4.00 TAGblock configuration sentences.

I, for one, would like to see the secs/msecs problem solved before GPSD
embarks on the enterprise of writing TAGblocks.

It might be too obvious, but observations of data suggest that you just count the number of digits?

- 10 digits = seconds
- 13 digits = millisecs

Note that I'm suggesting that we *add* these, not *consume* them from an upstream. As such you are free to make your own definition.

My request would be 13 digit millisecs.  My requirement is to be
a) able to play the stream back with moderate precision at some later time.
b) Filter multiple GPS units from the resulting mux'ed output NMEA stream

The use of a TAG block would work perfectly for my requirements... As long as we document what format WE use, I don't see a problem.

I found this interesting

Kind regards

Ed W

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